1. Field of the Invention
The present invention relates to a storage system and a storage control device.
2. Description of the Related Art
For example, data is controlled using relatively large-scale storage systems in order to handle large quantities of various types of data in government organizations, public offices, autonomous regional bodies, business enterprises, educational organizations and the like. For instance, such storage systems are constructed from disk array devices or the like. Disk array devices are constructed by disposing numerous storage devices in the form of an array; for example, a storage region based on an RAID (redundant array of independent disks) is provided. One or more logical volumes (logical units) are formed in a physical storage region provided by a storage device group, and these logical volumes are provided to a host computer (more specifically, to a data base program operating in a host computer). The host computer (hereafter abbreviated to “host”) can perform the reading and writing of data with respect to the logical volumes by transmitting specified commands.
With the development of an informationized society and the like, there has been a continual increase in the amount of data that must be managed. Consequently, there is a demand for storage control devices that offer higher performance and a larger capacity, and new types of storage control devices have been developed one after another in order to meet this market demand. There are two conceivable methods for introducing new types of storage control devices as storage systems. One is a method in which an old type of storage control device and a new type of storage control device are completely interchanged, so that a storage system is constructed from a completely new type of storage control device (Japanese Patent Publication No. 10-508967). The other method is a method in which a new type of storage control device is added to a storage system consisting of an old type of storage device, so that new and old types of storage devices are caused to coexist.
Furthermore, a technique in which the storage region of a physical device is controlled in sector units, and a logical device is dynamically constructed in sector units, is also known (Japanese Patent Application Laid-Open No. 2001-337850).
Moreover, a technique is also known which is devised so that when a logical device is constructed from a plurality of storage devices with different capacities, an area is formed in accordance with the storage device that has the smallest capacity, and an area is formed in accordance with the smallest capacity in the case of the remaining capacity as well (Japanese Patent Application Laid-Open No. 9-288547).
In cases where a complete transition is made from an old type of storage control device to a new type of storage control device, the function and performance of the new type of storage control device can be utilized; however, the old type of storage control device cannot be effectively utilized, and the introduction costs are also increased. On the other hand, in cases where an old type of storage control device and a new type of storage control device are used together, the number of storage control devices that construct the storage system is increased, and considerable effort is required in order to control and operate both the new and old storage control devices.
Furthermore, in cases where the response of the storage device in which the old type of storage control device is installed is slow, the performance of the overall system drops as a result of this old type of storage control device being connected to the storage system. For example, such cases include cases in which the old type of storage device is a device that involves mechanical operations (such as head seeking or the like), so that the mechanical operating time is long, cases in which the capacity of the data transfer buffer of the old type of storage device is small, and the like.
Furthermore, there may also be cases in which an old type of storage device cannot be utilized “as is”, as in combinations of open type storage devices and main frames, or servers to which only storage devices with specified functions can be connected.